ABSTRACT
Objective Rapamycin can improve characteristic pathology of AD by improving the level of autophagy.But, its internal mechanism still needs further study.This study was aimed to observe the protective effect of Rapamycin (RAPA) on the injury of rat pheochromocytoma (PC12) cells induced by β-amyloid protein25-35 (Aβ25-35).Methods PC12 cells in the logarithmic phase were randomly divided into 5 groups: control group(similar free-serum DMEM), model group, 10μmol/L RAPA treated group, 40μmol/L RAPA treated group and 160μmol/L RAPA treated group(add 10μmol/L, 40μmol/L RAPA, 160μmol/L respectively).Except the control group, each group was cultured with 20μmol/L Aβ25-35 to established the cell injury model.Results ①Compared with the survival rate of cells[(51.47±2.59)%] and the apoptosis rate of cells[(52.22±2.33)%] of the model group,the survival rate of cells in 10、40、160μmol/L RAPA treated groups and control group[(54.64±2.42)%, (64.79±2.91)% ,(56.50±2.55)% and (99.98±0.73)%] significantly increased, but the apoptosis rate of cells [(45.33±2.83)%, (36.89±2.85)%, (48.00±2.83)% and (3.33±2.45)%] significantly decreased(All P<0.05).②In model group,the expressions of p-PKB is 0.33±0.01, p-mTOR is 1.97±0.05, p-tau is 2.09±0.19.Compared with model group, in 10、40、160μmol/L RAPA treated groups and control group,these expressions of p-PKB (0.37±0.01, 0.42±0.01, 0.40±0.01 and 0.44±0.02) were significantly increased, however p-mTOR (1.64±0.05, 0.66±0.04, 0.35±0.01 and 0.62±0.01) and p-tau (2.02±0.15, 1.79±0.05, 1.86±0.06 and1.53±0.04) were decreased(All, P<0.05).ConclusionRAPA can increase Aβ25-35-induced PC12 cells viability, decrease cells apoptosis rates, and have a protective effect on Aβ25-35-induced PC12 cells death.The mechanism of its protective effect may be related to the inhibition of mTOR regulating PI3K/PKB/mTOR signal transduction pathway by negative feedback and the reduction of tau protein hyperphosphorylation.
ABSTRACT
beta-amyloid[Abeta] peptide consisting of 40 of 42 amino acids peptide is the principal constituent of senile plaques in Alzheimer`s disease. Recently, it has been demonstrated that this peptide and its constituent fragments are toxic to neuron. Basal forebrain cholinergic neurons are preferentially damaged early in the course of Alzheimer`s disease, and the degree of cholinergic decrement correlates well with the severity of dementia. Taking into consideration of toxic properties of Abeta and the selective vulnerability of the cholinergic system, possible effects of beta-amyloid on the cultured basal forebrain cholinergic neurons were tested. Our result showed tha Abeta1-40 induced marked neurodegenerative changes including loss of cell body and dystrophic neurites in the basal forebrain neuronal cultures at 20micrometer. Immunocytochemical study showed that Abeta1-40 causes apparent loss of choline acetyltransferase[ChAT] immunoreactivity and acetycholine esterase[AchE] positive neuritic intergrity in large basal forebrain cholinegic neurons. However, the number of ChAT immunoreactive neurons was not significantly decreased as compared to other neurons in mixed culture system. These results suggest that the basal forebrain neurons are not particularly vulnearable to Abeta and that preferential injury to basal forebrain cholinergic neurons in Alzheimer`s disease may be caused by some other medchanism.